Silurian biostratigraphy of the Cadia area, south of Orange, New South Wales

New Silurian fossil discoveries in the vicinity of Cadia Mine indicate ages younger than shown on recent maps. Limestone, intersected in drill core immediately above an unconformable contact with Late Ordovician volcanics of the mine sequence, yielded an early Wenlock conodont fauna including Pterospathodus amorphognathoides, P. procerus and P. rhodesi, together with Kockelella ranuliformis. A diverse shelly fauna of late Wenlock to early Ludlow aspect, dominated by brachiopods, is present in a slumped mudstone on the mine access road. South of the mine, in Rodds Creek valley, Silurian rocks are shown to occur as infaulted slices along the Werribee Fault. Limestone pods in this area contain conodonts (Coryssognathus dubius) indicative of a Ludlow age; a graptolite fauna from nearby siltstones includes Monograptus flemingii warreni, M. flexilis, Monoclimacis flumendosae flumendosae and Cyrtograptus ex, gr. C. rigidus, and is assigned to the lundgrenitestis Biozone (late Wenlock). The youngest graptolite assemblage (Pridoli) occurs in siltstones, tentatively correlated with the Wallace Shale, exposed in a shallow excavation east of Cadia Mine. This fauna, which includes Dictyonema sherrardae mumbilensis, Acanthograptus aculeatus neureaensis, Pristiograptus shearsbyi, P. cf. P. dubius, Monograptus parultimus minutus, M. microdon aksajensis and M. cf. M. yassensis, is younger than all known graptolite faunas from the nearby Four Mile Creek area, and provides the first Australian record of Monograptus microdon.